A conventional vacuum gripper assembly typically includes a generally flat plate provided with one or more vacuum gripping elements. The vacuum gripping element may be, for example, a plastic pad supported in an opening in the plate. The plastic pad is provided with an inlet for a vacuum hose and a plurality of smaller holes on the surface thereof through which suction is applied to create a local area of reduced pressure (vacuum). In order to avoid breakage of the wafers, which are often extremely thin, as well as to allow for variations in wafer thickness and/or positioning the pad is typically provided with a shock absorbing mechanism that allows the pad to move slightly in the X, Y and Z directions. In one example, the pad may be mounted to the plate using springs that allow damped motion of the pad within the opening in the plate. The ability of the pad to move slightly is intended to allow the pad to conform to the shape of the wafer in order to provide a secure vacuum grip on the wafer when the wafer is brought adjacent to the plate and the pad, as well as to prevent the pad sliding on the wafer when the wafer is brought in contact with another object and relative displacement between the wafer and the gripper may occur.
In conventional vacuum grippers, particularly of the type described, there appears to be a relatively large amount of wastage. This appears to occur in situations where the vacuum gripper does not adequately attach to the wafer. Attempts in the industry to resolve this issue have been unsuccessful. For example, providing a larger vacuum pressure to overcome missing the attachment to a wafer can result in additional breakage due to the strength of the vacuum pressure being too high.
Further, the assembly and the maintenance of a gripper having a pad supported by springs can also be expensive and time consuming.
As such there is a need for an improved vacuum gripper assembly.